Stator shroud and blade assembly



Nov. 22, 1955 cs. w. HARDIGG 2,724,544

STATOR SHROUD AND BLADE ASSEMBLY Filed May 25, 1951 GEORGE W. HARDIGGkw. mm)

ATTORNEY United States Patent STATOR SHROUD AND BLADE ASSEMBLYApplication May 25, 1951, Serial No. 228,176

2 Claims. Cl. 230-132 This invention relates to rotary elastic fluidapparatus such as compressors and turbines, and particularly to astationary vane row assemblyfor an axial-flow compressor.

In the construction of an axial-flow compressor for an aviation gasturbine engine, the stationary blade or vane assemblies, which areinterposed in complementary halves between the rotary blade stages,usually comprise concentric semicircular straps or shrouds of steelwhich are joined together by circumferentially spaced, radially disposedvanes. The vane ends are formed into tenons which are fitted intosuitably formed openings or slots punched in the respective shrouds, andthe entire assembly may then be either brazed or welded together. Withthe vane assemblies mounted in the compressor, the shrouds serve tofurnish boundaries for the air flow through the machine, to support theload which the air stream imposes on the vanes, and to impart rigidityto the vane structure to prevent the unsupported inner portion thereoffrom deflecting axially toward rubbing engagement with the adjacentrotary blades.

It is one object of the present invention to provide an improvedstationary vane assembly of the foregoing character having weight-savingfeatures of construction.

Another object of the invention is the provision of shroud elements forsuch an assembly having relatively thin portions interposed between theheavier punched portions thereof which receive the vanes, for minimizingthe total weight of steel utilized, without appreciably reducing therigidity or strength of the vane assembly.

A further object is to provide a shroud and vane struc ture in which theshrouds are crimped intermediate the vane-receiving slots therein, theair flow surfaces of the shrouds being machined or otherwise formed topresent smooth cylindrical boundaries, so that the thickness of eachshroud varies, comprising portions of maximum thickness at the points ofvane support and intervening webs of minimum thickness, which may beabout onehalf the maximum. Features of the improved shrouding thusconstructed subsist in the eflicient distribution of mass to conserveweight, the retention of the desired smooth air flow surfaces, and themaintenance of adequate strength and rigidity in the apertured vanesupporting areas.

These and other objects are effected by the invention as will beapparent from the following description and claims taken in connectionwith the accompanying drawings, forming a part of this application, inwhich:

Fig. 1 is a longitudinal view, partly in section, of a typical aviationgas turbine power plant, the compressor of which is adapted to beequipped with stationary vane and shroud structure constructed inaccordance with the invention;

Fig. 2 is an enlarged detail fragmentary sectional view taken along theline IIII of Fig. 1 and showing the improved vane and shroud structure;

Fig. 3 is a fragmentary perspective view of the vane and shroudstructure; and

Fig. 4 is a diagrammatic view illustrating one mode of formation of astationary vane shroud embodying the invention.

As shown in Fig. l, a typical gas turbine power plant 10, which isadapted to be mounted in an aircraft (not shown), may comprise agenerally cylindrical casing structure 11 having formed therein anaxial-flow passage 12 which extends from a frontal air intake 13 to arearwardly disposed jet nozzle 14, and conventional operating elementsfor effecting acceleration of fluid mass flow through the passage 12,including an axial-flow compressor 16. Other operating elements of theengine 10 not shown in the drawing include the usual combustionapparatus and a turbine for driving the compressor 16. In operation, airentering the intake 13 is supplied under pressure by the compressor 16to support combustion of fuel in the combustion apparatus, for which theresultant motive gases are expanded through the turbine and dischargedby way of the nozzle 14 in the form of a jet establishing a propulsivethrust.

The compressor 16 further comprises a rotor 17 carrying a plurality ofstages of radially extending blades including blades 18, which areinterposed between annular assemblies of stationary vanes including anassembly 19. A portion of the vane assembly 19 is illustrated inenlarged detail in Fig. 2 of the drawing, and comprises an outer arcuateshroud 20 and an inner arcuate shroud 21 which is held concentric withrespect to the outer shroud by a plurality of radially disposed vanes23, the end or tenon portions of which are engaged in slots 24 formed inthe respective shrouds, as shown in Fig. 3.

According to the invention, each of the shrouds 20 and 21 is of varyingthickness and is formed to provide areas of maximum mass in which thevane slots 24 are formed, interposed between areas of reduced massbetween the vanes. As best shown in Fig. 2, the outer shroud 20comprises thin web portions 20a interposed between relatively thickportions 20b, forming a smooth uniformly arcuate inner surface and anundulating outer surface, the outer surface, as shown, may be concavealong the web portions 20a and convex along the portions 2015, thusproviding the maximum mass of material adjacent the tenon-receivingslots 24. Similarly, the inner shroud 21 has a smooth peripheral surfaceand an undulating inner surface, forming alternate thin web portions,21a and thick portions 21b, so that the through passage 12 is definedbetween substantially smooth cylindrical walls. It will be understoodthat, in mounting the shroud and vane assembly 19 in the compressor 16,the outer shroud 20 will be engaged in a suitable annular groove (notshown) formed in the casing structure 11. Any suitable method may beemployed to form the above-described shrouds 20 and 21. For example, asillustrated diagrammatically in Fig. 4, the outer shroud 20 may berolled or otherwise formed into a generally circular shape but with aseries of crimps or corrugations which are equally spaced to correspondto the desired vane spacing. Upon the punching of the shroud to form thetenon slots 24, the shroud may be suitably mounted in a matrix and theinner side machined to form the relatively thin web portions and toprovide a smooth circular surface, as indicated by the dotted line 25,the material thus cut away representing the desired saving in weight.

While the invention has been shown in but one form,

it will be obvious to those skilled in the art that it is i not solimited, but is susceptible of various changes and modifications withoutdeparting from the spirit thereof.

What is claimed is: 1. An integral arcuate shroud member for an elasticfluid cooperative annular vane assembly, comprising a plurality ofregularly distributed web portions of minimum thickness interposedbetween and formed integral with a plurality of relatively thickportions, the thickness of said shrouds being uniform in any plane ofsection parallel to the axis of said assembly, each of said thickportions having extending therethrough a vane receiving opening, saidweb portions and said thick portions of the member presenting a smoothcontinuous arcuate surface on one face and an undulating surface on theopposite face.

2. The structure recited in claim 1 in which said any section isrectangular in shape and progressively increases in width from thecenter of said web portions to the center of said relatively thickportions.

References Cited in the file of this patent UNITED STATES PATENTS DeWein June 13, 1916 Lacey Oct. 24, 1933 Allen Mar. 31, 1942 Kroon June18, 1946 Allen et a1 July 12, 1949 Morley Nov. 22, 1949 Howard et al.Jan. 13, 1953 FOREIGN PATENTS Germany Oct. 16, 1910 Great Britain Jan.12, 1938

